[MCN] Not climate alone: Bumblebees take beating on multiple fronts

[Lance Olsen]

"We're hitting these animals with everything," he 
says. "There's no way you can nail a bee with 
neonicotinoids, invasive pathogens, and climate 
change and come out with a happy bee."

The loss of bee species could carry consequences 
for ecosystems and people. For instance, "plants 
that like their pollinators to be pretty loyal" 
could see declines in reproduction, says 
ecologist Laura Burkle of Montana State 
University, Bozeman. And given that wild bees 
help pollinate many crops, "we play with these 
things at our peril," Kerr says. "The human 
enterprise is the top floor in a really big 
scaffold. What we're doing is reaching out and 
knocking out the supports."
-----------------------------------
Bumblebees being crushed by climate change
By Cally Carswell 9 July 2015
http://news.sciencemag.org/biology/2015/07/bumblebees-being-crushed-climate-change
Science| DOI: 10.1126/science.aac8824

As the climate changes, plants and animals are on 
the move. So far, many are redistributing in a 
similar pattern: As habitat that was once too 
cold warms up, species are expanding their ranges 
toward the poles, whereas boundaries closer to 
the equator have remained more static.

Bumblebees, however, appear to be a disturbing 
exception, according to a study in Science today. 
A comprehensive look at dozens of species, it 
finds that many North American and European 
bumblebees are failing to "track" warming by 
colonizing new habitats north of their historic 
range. Simultaneously, they are disappearing from 
the southern portions of their range.

"Climate change is crushing [bumblebee] species 
in a vice," says ecologist Jeremy Kerr of the 
University of Ottawa in Canada, the study's lead 
author. The findings underscore the importance of 
conserving the habitat the insects currently 
persist in, says Rich Hatfield, a biologist with 
the Xerces Society for Insect Conservation in 
Portland, Oregon, who was not involved in the 
study. Where bumblebees vanish, the wild plants 
and crops they pollinate could also suffer.

To see how global climate change is affecting the 
bees, the researchers amassed a data set 
consisting of some 423,000 observations, dating 
back to 1901, of 67 bumblebee species in North 
America and Europe. Then they mapped large-scale 
changes in the species' territories and in their 
"thermal ranges"-the warmest and coolest places 
the bees live. They also built statistical models 
to test whether any range shifts were best 
explained by climate change, or whether two other 
factors-changes in land cover and the use of 
pesticides such as neonicotinoids, which have 
been implicated in smaller-scale bee 
declines-also played a key role.

Overall, they found that some bumblebees have 
retreated as many as 300 kilometers from the 
southern edge of their historic ranges since 
1974. The rusty patched bumblebee (Bombus 
affinis), for instance, has disappeared from 
parts of the southeastern United States. Southern 
species are also retreating to higher elevations, 
shifting upward by an average of about 300 meters 
over the same time period. Meanwhile, few species 
have expanded their northern territories. And it 
turned out that climate change was the only 
factor that had a meaningful impact on the 
large-scale range shifts. (Data on pesticide use 
were available only in the United States, 
however, and the study did not examine whether 
populations were growing or shrinking.)

One clue to the importance of climate: Bumblebee 
ranges began shrinking "even before the 
neonicotinoid pesticides came into play in the 
1980s," says ecologist and coauthor Alana Pindar, 
a postdoctoral fellow at the University of Guelph 
in Canada. She says the retreat from southern 
territories is "a huge loss for bumblebee 
distributions" and happened surprisingly quickly. 
The researchers believe the retreat-and the move 
to higher elevations-may reflect the fact that 
bumblebees evolved in cooler climates than many 
other insects that haven't yet lost ground, and 
so are especially sensitive to warming 
temperatures.

More mysterious is their failure to push north. 
"What we can infer is that temperature in the 
northern latitudes is not what's limiting their 
spread," says Ignasi Bartomeus, a researcher at 
Spain's Estación Biológica de Doñana in Seville, 
who was not involved in the study. Differences in 
daylight or food could hamper a march north, or 
bumblebee populations may simply be too 
slow-growing to quickly expand.
Many bumblebees form small colonies, Kerr 
explains, limiting their ability to spread 
quickly. In contrast, species with high 
population growth rates are "more likely to be 
able to establish a new colony that represents a 
measurable difference in geographic range." He 
notes that one outlier in the study, the 
buff-tailed bumblebee (Bombus terrestris), one of 
Europe's most common species, is known for its 
reproductive success and has moved north. The 
species "is kind of like the dandelion of the 
bumblebee world," he says.

So far, says Bartomeus, the most common bumblebee 
species seem to be the most resilient. But "we 
have a lot of losers," he cautions, including 
species that have specialized habitat 
requirements. And climate change could further 
strain species already struggling with dwindling 
habitat and other pressures, Kerr says. "We're 
hitting these animals with everything," he says. 
"There's no way you can nail a bee with 
neonicotinoids, invasive pathogens, and climate 
change and come out with a happy bee."

The loss of bee species could carry consequences 
for ecosystems and people. For instance, "plants 
that like their pollinators to be pretty loyal" 
could see declines in reproduction, says 
ecologist Laura Burkle of Montana State 
University, Bozeman. And given that wild bees 
help pollinate many crops, "we play with these 
things at our peril," Kerr says. "The human 
enterprise is the top floor in a really big 
scaffold. What we're doing is reaching out and 
knocking out the supports."

-- 
==========================================================
"Even doubling our current rate of 
decarbonisation, would still lead to emissions 
consistent with 6 degrees of warming by the end 
of the century. To give ourselves a more than 50% 
chance of avoiding 2 degrees will require a 
six-fold improvement in our rate of 
decarbonisation."

Leo Johnson
Partner, Sustainability and Climate Change, PricewaterhouseCoopers
"Too late for two degrees? Low carbon economy index" November 2012
<<https://www.thepmr.org/system/files/documents/Low%20Carbon%20Economy%20Index%202012.pdf>>
===================================================================
"Š the serious meaning in a concept lies in the
difference it will make to someone if it is true."

William James (1842 -1910)
Pragmatism. Meridian Books, 1955






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